drive system for interconnecting attachment devices and handheld rotary power tools

ABSTRACT

Embodiments of the present invention are directed to a drive system for releasably interconnecting a motor shaft of a rotary hand held power tool and an input shaft of an attachment device that is mounted thereon, the system comprising, an elongated flexible drive shaft connected to the input shaft of the attachment device, the flexible drive shaft having an outer end portion with a non-circular cross-section configured to engage a complementarily shaped cavity of an output shaft operatively attached to the power tool motor shaft, an elongated output shaft operatively connected to the motor shaft of the power tool, the output shaft having a generally cylindrical outer configuration along its length and having a rearward mounting portion for attachment to the motor shaft, an intermediate portion having the complementarily shaped cavity for receiving the flexible drive shaft and a forward portion with an enlarged concentric opening for receiving and guiding the outer end portion of the flexible drive shaft into the cavity during mounting the attachment device on the power tool.

BACKGROUND OF THE INVENTION

The present invention generally relates to small handheld power tools,and more particularly to a dust collection attachment system for suchtools.

Small handheld power tools that perform drilling, sawing and other typesof cutting and the like are known in the prior art and have been widelyused by hobbyists, artisans, tradesmen and others in a wide variety ofapplications. Such rotary hand tools generally have a motor with arotary output shaft that extends from a nose portion that is morerecently configured to connect to various accessories or attachmentdevices. Some of these rotary hand tools are quite powerful for theirsize and are used by tradesmen in the building trades as spiral sawsthat use a side cutting rotary bit to penetrate and rapidly cut holes indrywall sheets and other materials for electrical switches, outlets,light fixtures and the like.

As is known in the art, such rotary hand tool tasks can be more easilyperformed by using an attachment device that is attached to the tool.For example, a right angle attachment device may be mounted on the powertool and such devices may be configured to drive a circular saw blade, agrinding wheel, a sanding pad or polishing pad.

Such a right angle attachment device has an input shaft that must beinterconnected with the output shaft of the tool when the attachmentdevice is mounted on the tool. The interconnection can present problemsresulting from the relatively high speed operation, together withmisalignment of the two shafts, which can create undesirable vibration.A drive system that minimizes such vibration and facilitates quick andeasy mounting and removal of such attachment devices is desirable.

SUMMARY OF THE INVENTION

Embodiments of the present invention are directed to a drive system forreleasably interconnecting a motor shaft of a rotary hand held powertool and an input shaft of an attachment device that is mounted thereon,the system comprising, an elongated flexible drive shaft connected tothe input shaft of the attachment device, the flexible drive shafthaving an outer end portion with a non-circular cross-section configuredto engage a complementarily shaped cavity of an output shaft operativelyattached to the power tool motor shaft, an elongated output shaftoperatively connected to the motor shaft of the power tool, the outputshaft having a generally cylindrical outer configuration along itslength and having a rearward mounting portion for attachment to themotor shaft, an intermediate portion having the complementarily shapedcavity for receiving the flexible drive shaft and a forward portion withan enlarged concentric opening for receiving and guiding the outer endportion of the flexible drive shaft into the cavity during mounting theattachment device on the power tool.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view taken from the front left of a rotaryhandheld power tool that incorporates an embodiment of the presentinvention;

FIG. 2 is an isometric view of a right angle attachment device whichalso incorporates an embodiment of the present invention, with theattachment device being capable of being mounted to the power tool shownin FIG. 1;

FIG. 3 is a cross section taken through the center of the output shaftof the tool shown in FIG. 1;

FIG. 4 is an isometric view of a portion of the output shaft shown inFIG. 3, having a collet inserted in the outer end thereof;

FIG. 5 is a view similar to FIG. 4 wherein a collet nut is attached tothe output shaft;

FIG. 6 is a cross-section taken generally through the middle of theoutput shaft, collet and collet nut shown in FIG. 5;

FIG. 7 is a cross-section of a portion of the power tool shown in FIG.1, with the attachment device shown in FIG. 2, with both being shown incross section generally through the center thereof, but illustrating theattachment device in position where it is beginning to be mounted to thepower tool; and

FIG. 8 is a cross-section similar to FIG. 7, but showing the attachmentdevice attached thereto, and more particularly showing the attachmentdevice mounted and secured to the power tool.

DETAILED DESCRIPTION

The present invention is directed to a drive system for releasablyinterconnecting an output shaft of a rotary handheld power tool or thelike and an input shaft of an attachment device that is mounted on thepower tool. Such a drive system may be particularly desirable for smallhandheld power tools having an elongated housing with a rotary outputshaft is provided at a nose portion thereof, wherein the nose portion isconfigured to attach an attachment device thereto. Such an attachmentdevice may be a right angle drive which has its own output shaft thatmay drive a circular saw blade, grinding wheel, or the like.

The attachment device has an input shaft that must be interconnectedwith the output shaft of the power tool and it has been known that theinterconnection of these two components can produce undesirable levelsof vibration at relatively high operating speeds if there ismisalignment of the shafts. Such vibration can be reduced by having theinput shaft of the attachment device be made of a flexible material,which can be a multiplicity of parallel wires that are compressed underhigh pressure to form a shaft having a non-circular end, and preferablya square end, for engagement with the output shaft of a power tool, butwhich is sufficiently flexible that it can compensate for slightmisalignment and significantly reduce vibration that would otherwiseoccur. Such flexible shafts are known in the prior art.

Embodiments of the drive system of the present invention greatlyfacilitate easy and fast mounting of an attachment device to such apower tool without interfering with a common use of the power tool wherea collet and collet nut can be installed to attach standard tool bits tothe output shaft, such as spiral saw bits and the like.

Turning now to the drawings and particularly FIG. 1, an elongated powertool, indicated generally at 10, is shown and has an elongated housing,indicated generally at 12, and a nose portion, indicated generally at14. The housing has a top surface 18, side surfaces 20 and a bottomsurface 22 and a motor is contained within the housing. The size of thehousing 12 is such that most users can grip the tool with one hand withtheir fingers curling around under the bottom portion 22. When a personis holding the tool 10 as described, their thumb is in position tooperate a switch 32 which turns on the motor for operating the tool. Theswitch 32 is preferably designed so that can be slidingly moved betweenits ON and OFF positions. The tool 10 shown in FIG. 1 has a power cord34 that can be plugged into a source of AC power. It should beunderstood that power tools similar to that shown in FIG. 1 mayincorporate battery packs and in such event, they may be slightlylarger. The present invention is suited for use with power tools thatuse such power packs.

The nose portion 14 has an attachment interface that is described in aco-pending patent application entitled “AN ATTACHMENT INTERFACE FORROTARY HAND TOOLS”, Ser. No. ______, that is filed concurrently withthis application and is incorporated by reference herein. The noseportion has a cylindrical wall, indicated generally at 40, which hasouter threads 42, as well as an inner surface that has a number of keys44 that are configured to engage complementary shaped keys on anattachment device that may be mounted on the nose portion 14.

The tool 10 has an output shaft, indicated generally at 50, which isbest shown in FIGS. 1 and 3 which is configured to be able to accept acollet and collet nut for mounting a cylindrical tool bit, such asspiral bit, for example, and is also configured to accept an input shaftof an attachment device that can be mounted on the nose portion 14 ofthe tool 10.

The output shaft 50 is best shown in FIG. 3 and has a rearward (i.e.,the left end) mounting portion, indicated generally at 52, forattachment to a drive shaft of the motor of the power tool 10, which isan armature shaft of the motor, an intermediate portion, indicatedgenerally at 54, that is configured to receive an input shaft of theattachment device and a forward portion, indicated generally at 56, thatis configured to initially guide the input shaft of an attachment deviceinto the intermediate portion 54 as well as interact with a collet andcollet nut for mounting a tool bit to the output shaft 50. It is notedthat the three portions, i.e., the mounting portion, intermediateportion and forward portion are approximately equal in length, althoughthe proportions of each relative to the other may be varied as desired.

With regard to the mounting portion 52, it has a central bore 60 thathas a chamfered end surface 62 to facilitate entrance by the armatureshaft 64 (see FIGS. 7, 8) of the tool motor. The bore 60 preferably isonly slightly larger than the outer diameter of the armature shaft 64,so that it is securely fastened therein after the mounting portion iscompressed or crimped onto the shaft 64. The mounting portion 52 alsohas radial openings 66, each with a chamfered outer surface 68 which issized to receive a pin of a locking mechanism for locking the outputshaft from rotation so that a tool bit can be firmly secured in a colletby tightening a collet nut.

The mounting portion 52 has the largest diameter of any of the portions52, 54 or 56 and the interface between the mounting portion 52 and theintermediate portion 54 defines an annular shoulder 72. The intermediateportion 54 has an outer surface 74 that has a diameter slightly largerthan the outer surface 76 of the forward portion 56 so that a frontbearing (104, FIGS. 7 and 8) can be easily slipped on the forward end 56without interference with the inside surface of the inner race of such abearing and be mounted on the outer surface 74 of the intermediateportion 54. The outer surface 74 also has an annular groove 78 forreceiving a retaining ring (112, FIGS. 7 and 8) that holds the frontbearing in place.

The interface between the intermediate portion 54 and the forwardportion 56 defines another shoulder 80 and the smallest outside diameterof the entire output shaft 50 is surface 82. The surface 76 is slightlylarger in diameter and it contains threads which are not shown but arewell known to those of ordinary skill in the art for screwing orthreading a collet nut onto the forward portion of the output shaft 50.

The bore 60 of the mounting portion 52 is in communication with a cavity84 that has a preferably square cross section. In this regard, the crosssectional configuration of the cavity 84 can be any non-circular shapethat is complementary to the shaft that is inserted into it. This cavity84 has a length sufficient to hold a complementary shaped shaft (98,FIGS. 7 and 8) that may be inserted into the forward end portion 56. Itshould be understood that any noncircular type of cross section thatwill enable rotation of the output shaft 50 to positively rotate a shaftthat is located within it may be used. Thus, a five sided or hexagonalor other noncircular cross-sectional shape may be used. However a squarecross-section is preferred because it does not require close tolerancesbetween the size of the cavity 84 and the size of an input shaft thatmay be inserted in it.

The forward end portion 56 has an initial cylindrical bore portion 86 aswell as a smaller step down portion 88 that in turn merges with aninclined conical portion 89 as well as a smaller diameter portion 91that communicates with the cavity 84. The progressively smaller insidediameters from the outer end extending inwardly facilitate easy initialinsertion of an input shaft from an attachment device and effectivelyguides the same so that it can be inserted into the cavity 84.

An attachment device is indicated generally at 90 in FIG. 2 andcomprises a right angle saw attachment device which can be mounted onthe tool. The device will not be described in detail inasmuch as thepresent invention deals with only the interconnection of it with thetool on which it is mounted. In this regard, the device 90 has a mainhousing 92 and a rotatable collar 94 with internal threads 96 that aresized and configured to thread the collar 94 onto the threads 42 of thenose portion 14 of the powertool 10.

The device 90 has an input shaft 98 which has a square outer end 100that is sized and configured to fit within the cavity 84. The inputshaft 98 is preferably permanently secured such as being crimped in agear shaft in the attachment device 90 so that it will not be lost whenthe attachment device is separated from the power tool 10. The length ofthe shaft 98 is sufficiently long so that the outer square cross-sectionend portion 100 will penetrate the output shaft 50 so that itsubstantially fills the cavity 84 when the device is secured to the tool10.

In this regard, the view of FIG. 7 shows the device with the end portion100 penetrating into the forward portion 56 of the output shaft 50before the collar 94 is threaded or screwed onto screws 42 of the noseportion 14 as shown in FIG. 7. When it is tightened as shown in FIG. 8,the square end portion 100 is fully inserted into the cavity 84.

Parenthetically, FIGS. 7 and 8 diagrammatically show a front bearing 104with inner and outer races 106 and 108 with ball bearings 110therebetween and a retaining clip 112 is located in the annular groove78. It is also noted that the mounting portion 52 is not completelyshown in these drawings.

As previously mentioned, the forward portion 56 is configured to receivea collet and to this end, and referring to FIGS. 4, 5 and 6, a collet120 is shown to fit within the bore 86. The collet 120 is only partiallyinserted in the bore 86 in FIG. 4. A collet nut 122 is configured to bethreaded onto the threaded surface 76. As is typical, the collet nut hasan inclined inner surface 124 that interacts with an inclined outersurface 126 on the collet and another inclined surface 128 engages thesurface 89 of the forward portion 56 as is known to those of ordinaryskill in the art. When the collet nut 122 is tightened, the internaldiameter of the central opening is reduced to provide a holding force ona tool bit inserted in the collet 120.

While various embodiments of the present invention have been shown anddescribed, it should be understood that other modifications,substitutions and alternatives are apparent to one of ordinary skill inthe art. Such modifications, substitutions and alternatives can be madewithout departing from the spirit and scope of the invention, whichshould be determined from the appended claims.

Various features of the invention are set forth in the following claims.

1. A drive system for releasably interconnecting a motor shaft of arotary hand held power tool and an input shaft of an attachment devicethat is mounted thereon, said system comprising: an elongated flexibledrive shaft connected to the input shaft of the attachment device, saidflexible drive shaft having an outer end portion with a non-circularcross-section configured to engage a complementarily shaped cavity of anoutput shaft operatively attached to the power tool motor shaft; anelongated output shaft operatively connected to the motor shaft of thepower tool, said output shaft having a generally cylindrical outerconfiguration along its length and having a rearward mounting portionfor attachment to said motor shaft, an intermediate portion having saidcomplementarily shaped cavity for receiving said flexible drive shaftand a forward portion with an enlarged concentric opening for receivingand guiding the outer end portion of said flexible drive shaft into saidcavity during mounting the attachment device on the power tool.
 2. Adrive system as defined in claim 1 wherein said non-circular crosssection of said flexible drive shaft and the cross section of saidcomplementarily shaped cavity are generally square.
 3. A drive system asdefined in claim 1 wherein the rotary tool comprises an elongatedhousing with a nose portion having an opening concentric for accessingsaid output shaft, the nose portion including a transition portion withan inclined outer surface extending radially inwardly toward the motorshaft and a generally cylindrically shaped wall extending from thetransition portion concentrically and forwardly and having a pluralityof screw threads formed in an outer surface of the wall, and theattachment device has a screw threaded collar rotatably attached theretofor mounting the attachment device to the nose portion of the powertool, wherein the collar is screwed onto the screw threads of the wallof the nose portion to secure the same thereto, the outer end portion ofsaid flexible drive shaft extending forwardly of the attachment device adistance sufficient to enter said enlarged concentric opening of saidforward portion of said output shaft before the collar is screwed ontothe screw threads of the wall of the rotary tool.
 4. A drive system asdefined in claim 1 wherein said output shaft has a cylindrical openingsized to snugly accept said motor shaft, said output shaft beingattached to the motor shaft by crimping the output shaft against themotor shaft.
 5. A drive system as defined in claim 1 wherein the inputshaft of the attachment device is cylindrically shaped and has acylindrical concentric opening in the outer end thereof, said flexibledrive shaft is connected to said input shaft by inserting the same intosaid opening and crimping the input shaft against said flexible driveshaft.
 6. A drive system as defined in claim 1 wherein said each of saidmounting portion, said intermediate portion and said forward portions ofsaid output shaft comprises approximately one third of the length ofsaid output shaft.
 7. A drive system as defined in claim 1 wherein theoutside surface of a substantial amount of said forward portion is screwthreaded.
 8. A drive system as defined in claim 7 wherein said threadedoutside surface has a slightly larger diameter than the adjacent surfacerearwardly thereof.
 9. A drive system as defined in claim 8 wherein arearward section of said enlarged concentric opening of said forwardportion has an inwardly tapered surface for receiving an end portion ofa collet that has an opposite end portion that extends forwardly beyondthe end surface of said forward portion for clamping a tool bit.
 10. Adrive system as defined in claim 9 further comprising a collet nut sizedand configured to be screwed onto said screw threads of said outsidesurface of said forward portion.
 11. A drive system as defined in claim1 wherein said mounting portion of said output shaft has at least oneradial opening in the outer surface thereof configured to receive aportion of a shaft lock mechanism for preventing rotation of the toolmotor shaft.
 12. A drive system as defined in claim 3 wherein saidintermediate portion has an outside diameter that is larger than theoutside diameter of said threaded outside surface and said mountingportion has an outside diameter that is larger than the outside diameterof said intermediate portion to form an annular shoulder at theinterface between said portions, said system further comprising abearing having inner and outer races, said inner race of which fits onsaid outside surface of said intermediate portion and bears against saidshoulder, said outer race of which fits within an inside surface of saidcylindrically shaped wall, said bearing providing stability counteringside forces applied to said output shaft.
 13. A drive system as definedin claim 12 wherein said intermediate portion has at least one annulargroove positioned adjacent an end of said race opposite said end bearingagainst said shoulder, said groove being configured to receive a clipfor holding the bearing in place.
 14. A drive system as defined in claim1 wherein said elongated flexible drive shaft is formed of a pluralityof strands of flexible steel wire that are fused together under highpressure and heat to form a unitary shaft.
 15. A drive system as definedin claim 1 wherein said output shaft and said attachment device inputshaft are made of steel.
 16. A drive system as defined in claim 1wherein the nose portion of housing of the power tool is made ofaluminum.